<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<style>
    .box{
        box-sizing: border-box;
        height: 50px;
        width: 50px;
    }
    .box:hover{

        border: 10px solid red;
    }
</style>
<body>

<div class="box">

</div>
</body>
</html>